There are different types of wall coatings: paint, wallpaper, or coatings projected over a greater thickness than paint, and to which it is possible to give a relief by means of a spatula or of a honeycombed roller. Although these coatings are liked due to their decorative character, they have, nevertheless, the disadvantage of being in a single colour, generally white, which limits the decorative effects likely to be obtained.
There are also coatings with a decorative appearance which are characterised by the presence of coloured grains, the latter being coloured grains of sand either coloured naturally, or artificially. These grains are overcoated with a binder of the latex type and deposited onto a substrate such as a wall, by means of a hawk. Over and above the fact that this method of application is long and fastidious, the quantity of coloured sand deposited per square meter is large, due to the rough granulometry of the sands and to the fact that the substrate must be entirely covered over. Thus the weights per square meter deposited can rise according to the grain sizes from 2 to more than 8 kg/m.sup.2.
Another solution to obtain a coating comprising coloured particles consists in applying a background layer on a substrate, then to project by blowing over this substrate, which is still wet, dry multicoloured flecks, and finally to apply a layer of varnish. This process is extremely fastidious to implement since a high proportion of the flakes, at least half, fallen on the ground, must be recovered and projected again, with the risk of seeing the flakes being loaded with impurities. Moreover, a complementary brushing of the wall must be carried out before applying the varnish.
In both cases, the techniques are long and difficult to implement, allowing only the coating, in a single operation, of small surfaces.